Conventionally, an epoxy resin has been widely used as an epoxy resin composition in combination with a curing agent in the electronic materials field. In such an electronic materials field, in order to be applied to, for example, a high refractive index layer of an anti-reflective coating (for example, an anti-reflective coating for liquid crystal displays), an optical thin film (for example, a reflection plate), a sealing material for electronic parts, a printed circuit board, and an interlayer dielectric material (for example, an interlayer dielectric material for built-up printed boards), forming materials are required to have performances such as high adhesion to a substrate, hard coating properties, high heat resistance, and high transparency to visible light.
In general, a crystalline epoxy resin has a rigid main chain skeleton or is multifunctional and hence has high heat resistance. Therefore, such a resin is used in a field requiring heat-resistant reliability, for example, in an electrical and electronic field.
However, in some fields to which such an epoxy resin is applied, molding cannot be performed except by, for example, casting using a liquid composition. The crystalline epoxy resin is limited to be applied to the molding using a solid material, for example, transfer molding, and the application range is limited.
Conventionally, an epoxy resin used for liquid molding such as casting is a liquid epoxy resin. Hence, such an epoxy resin is difficult to achieve sufficiently satisfactory improvement of physical properties of a cured product, such as heat resistance of which requirement has been increased in fields such as adhesion, casting, sealing, molding, and lamination. To address this, there is an increasing demand for liquefaction of a crystalline multifunctional epoxy resin that can provide a cured product having physical properties such as high heat resistance. In addition, there is a demand for photo- or heat-curing of the liquid epoxy resin.
Meanwhile, there has been disclosed an epoxy resin that is obtained by liquefaction of a highly crystalline epoxy compound such as tris-(2,3-epoxypropyl)-isocyanurate of which some of epoxy groups are esterified to reduce crystalline properties (see Patent Document 1).
There has been also disclosed a compound having a triazinetrione ring to which an epoxy ring is bonded through a long chain alkylene group (see Patent Document 2).
There have been further disclosed an epoxy compound having a triazinetrione ring to which an epoxy ring is bonded through a long chain alkylene group and an epoxy resin composition using the epoxy compound (see Patent Documents 3, 4, and 5).
In addition, there have been disclosed an epoxy compound having a triazinetrione ring to which an epoxycyclohexyl group is bonded through an oxyalkylene group and an epoxy resin composition using the epoxy compound (see Patent Document 6).